As part of the predator control efforts of the early 1900s, state wildlife veterinarians intentionally released Sarcoptes scabiei, the mite that causes sarcoptic mange, a chronic infection that induces hair-loss, into gray wolves (Canis lupus) and coyotes (Canis latrans) in the northern Rocky Mountains. Wolves were successfully extirpated from the region by the 1930s and were reintroduced into Yellowstone National Park in 1995. Sarcoptes scabieipersisted in the absence of wolves, and by 2007, it invaded Yellowstone’s wolf population where we have since followed its dynamics and impacts. Within this system, our research seeks to address the following broad questions: (1) What are the spatial and temporal patterns of mange invasion within the wolves of Yellowstone? (2) What are the individual and population-level impacts of this parasite on its host? (3) What are the drivers of heterogeneity observed in infection risk, severity, and outcome? We address these questions using a long-term dataset on wolf demographics, mange infection status, and thermal imagery of wolves infected with sarcoptic mange.
Sarcoptic mange first appeared among wolves in Yellowstone in 2007 and reached its initial epidemic peak by 2010, affecting approximately 20% of the park-wide population, but with regional prevalences of 40%, and within-social-group prevalences of 60%. Sarcoptic mange has since persisted within the wolf population with seasonal and sporadic fluctuations in prevalence. The patterns of spatial spread have been positively associated with wolf connectivity and density, with the areas of highest resource quality and wolf density experiencing the most rapid and extensive levels of infection and parasite-associated declines. Our research using thermal cameras suggests that wolves suffering from mange-induced hair-loss are expending considerably more energy thermoregulating in winter months, which may translate to behavioral changes, increased food intake, and reduced body condition. We demonstrate that the mite can have profound impacts on wolf survival, but only when wolf group size is small or the prevalence of the mite within the group is high. We document recovery from infection, but find no evidence for long-term immunity. Ongoing monitoring aims to disentangle the relative impacts of mange and other parasites from the effects of food resources on the population dynamics of wolves in Yellowstone. While the success of wolf reintroduction appears not to have been jeopardized by sarcoptic mange, we discuss insights from our system as they apply more broadly to carnivore conservation and management.